The Exhibit below illustrates how an Ethernet frame is sent. PC1 will send an Ethernet frame, that is received and forwarded by Switch1. Switch1 forwards the frame to Router1. Router1 also forwards the packet to Router2 via serial link. Router2 will then forward the frame to Router3 via serial link, after which Router3 will forward the packet to the destination, PC2. Router3 and PC2 are connected to the same Ethernet hub, called Hub1.
Which networking devices can be used to examine the QoS field?
A.
all devices
B.
all routers
C.
the hub and switches
D.
all devices except the hub
E.
Switch1 only
F.
Switch1 and Router1